Recoilless open chamber gun



May 27, 1969 D. DARDICK RECOILLESS OPEN CHAMBER GUN Sheet 01'3 FiledSept. 1, 1967 INVEN'I 0R Dmf/o lineal CK y 27, 1969 D. DARDICK 3,446,111

RECOILLESS OPEN CHAMBER GUN Filed Sept. 1. 1967 Sheet 3 of 3 I I02 H5Ha. (I03 8 I N VEN TOR v DOV/D .DAQD/CK kam w May 27, 1969 D. DARDICK3,446,111

RECOILLESS OPEN CHAMBER GUN Filed Sept. 1, 1967 Sheet 3 of 3 D4 we.DAPO/CK INVENTOR.

United States Patent O 3,446,111 RECOILLESS OPEN CHAMBER GUN DavidDardick, Palos Verdes Peninsula, Calif., assignor to TRW Inc., RedondoBeach, Calif., a corporation of Ohio Filed Sept. 1, 1967, Ser. No.664,979 Int. Cl. F41f 3/02, 15/00 US. Cl. 891.7 7 Claims ABSTRACT OF THEDISCLOSURE A recoilless open chamber gun having rearwardly openingventuri means through which a portion of the high pressure propellantgas generated during firing exits at high velocity to produce on the guna counter-recoil force equal and opposite to the recoil force exerted onthe gun during firing.

REFERENCE TO COPENDING APPLICATIONS Reference is made herein tocopending applications Ser. No. 671,910, filed Sept. 1, 1967, andentitled, Sealed Open Chamber Breech Mechanism and Caseless AmmunitionTherefor, Ser. No. 665,136, filed Sept. 1, 1967, and entitledSemicombustible Ammunition for Open Chamber Breech Mechanism, and Ser.No. 665,160, filed Sept. 1, 1967, and entitled, Ammunition Improvementsto Permit Firing of a Conventional Closed Chamber Cartridge in an OpenChamber Breech Mechanism.

BACKGROUND OF THE INVENTION Field of the invention Prior art It is wellknown in the art that all weapons, when fired, experience a rearwardrecoil force which is equal and opposite to the forward propulsion forceexerted on the projectile for propelling the latter forwardly throughthe gun bore. In small caliber weapons, such as rifles and pistols, themagnitude of this recoil force is relatively small and can be sustainedby the person firing the weapon. In larger caliber weapons, on the otherhand, the recoil force is relatively large and must be absorbed orneutralized in some way. For example, in some large caliber weapons,i.e., recoiling weapons, the breech mechanism is supported by a cradlefor recoil and counter-recoil movement, and the kinetic energy of therecoil breech mechanism following firing is absorbed by counter-recoilmeans which arrest the breech mechanism with a cushioning action andthen return the mechanism to battery position. In other larger caliberweapons, i.e., recoilless weapons, a portion of the high pressurepropellant gas generated during the firing is directed throughrearwardly opening venturi means in the breech end of the weapon toproduce on the weapon a counter-recoil force substantially equal inmagnitude and opposite in direction to the recoil force on the weapon.The present invention is concerned with this latter technique ofcounteracting recoil force.

ICC

Conventional recoilless weapons, while effective to neutralize therecoil force produced during firing, are deficient in that they areincapable of automatic high rate firing. This deficiency results fromthe relatively long length of recoilless ammunition necessary to containthe additional propellant required to develop the counter-recoil thrustand to the four step firing cycle employed in conventional automaticweapons. Thus, the firing cycle of such weapons involves initial lateralinfeed movement of each round into the breech, axial insertion orramming of the round into the firing chamber, axial removal orextraction of the spent cartridge case from the chamber after firing,and final lateral ejection of the cartridge case. This necessity ofaxially ramming each round into and axially extracting the spentcartridge case of each round from the firing chamber, coupled with therelatively long overall length of the conventional recoilless ammunitionround, precludes high rate automatic firing of conventional recoillessweapons.

The above-noted disadvantages which attend conventional closed chamberguns and their four step firing cycle are avoided in guns having aso-called open chamber breech mechanism. Guns of this type, for example,are disclosed in Patents Nos. 2,983,223; 3,041,938; 2,831,140;2,847,784; 3,046,890. Generally speaking, such an open chamber gun ischaracterized by an open chamber breech mechanism including a breechframe having a chamber containing a rotary carrier or cylinder with oneor more firing chambers which open laterally through the circumferenceand longtiudinally through the forward end of the cylinder. The cylinderis supported on the breech frame for rotation or oscillation tosequentially locate each firing chamber in an ammunition infeedposition, a firing position, and, when firing cased ammunition, acartridge case ejection position. When in infeed position, the open sideof the firing chamber registers with a lateral ammunition infeed openingin the breech frame to permit lateral infeed movement of an ammunitionround into the chamber. When in firing position, the firing chamber isclosed by the breech frame and opens forwardly to the gun bore tocondition the breech mechanism for firing the round in the chamber. Whenin ejection position, the open side of the firing chamber registers witha lateral ejection opening in the breech frame to permit lateralejection of the spent cartridge case from the chamber after firing. Aprimary advantage of an open chamber breech mechanism, then, is itseffectively two-step firing cycle involving initial lateral infeedmovement of each ammunition round to firing position and final lateralejection of each spent cartridge case from firing position. As aconsequence, the total travel of each ammunition round through an openchamber breech mechanism from infeed to ejection is independent of andbut a fraction of the overall length of the round and is substantiallyless than the total ammunition travel through a conventional closedchamber breech mechanism. In one type of open chamber gun, referred toherein as a fixed barrel gun, each gun barrel is secured to and remainsstationary with the breech frame, and each firing chamber isstationarily aligned with the barrel during firing. In another type ofopen chamber gun, referred to herein as a rotary barrel gun, each barrelis secured to and rotates continuously with the cylinder, even duringfiring, to achieve a high firing rate.

It is now evident, therefore, that the open chamber concept is uniquelyadapted to an automatic, high rate recoilless firing action. The openchamber breech mechanisms, disclosed in the aforementioned priorpatents, however, are incapable of such recoilless firing action owingto the fact that they lack means for utilizing a portion of thepropellant gas generated during firing to produce a counter-recoilthrust on the breech mechanism.

SUMMARY OF THE INVENTION This invention provides an open chamber gunwhich is designed to provide a recoilless firing action. To this end,the open chamber gun of the invention comprises a basic open chamberbreech structure essentially identical to those disclosed in the earliermentioned patents. According to the present invention, the breech frameis provided with rearwardly opening venturi means which communicate withthe firing chamber when the latter occupies its firing position. When anammunition round is fired in the chamber, a portion of the high pressurepropellant gas issues at high velocity through the venturi means toproduce on the gun a counter-recoil thrust substantially equal andopposite to the recoil force exerted on the gun. In one disclosedembodiment of the invention, for example, the firing chamber and venturimeans communicate via propellant gas plenums which extend longitudinallythrough the breech frame firing strap and cylinder and communicatelaterally to the firing chamber through ports in the inner wall of thefiring strap and the side walls of the firing chamber. In anotherdisclosed embodiment of the invention, the venturi means communicatewith the firing chamber through passages in the rear Wall of thechamber.

It is significant to recall here that the present recoilless openchamber gun may fire cased, semi-combustible, and caseless ammunition.In this regard, attention is directed to the earlier mentioned copendingapplications and patents which disclose these various types ofammunition. Also, the gun may have either a fixed barrel or a rotarybarrel construction.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a side elevation, partly in section, of a fixed barrelrecoilless open chamber gun according to the invention;

FIG. 2 is an enlarged section taken on line 22 in FIG. 1;

FIG. 3 is a fragmentary section taken on line 3-3 in FIG. 2;

FIG. 4 is a rear end view of the gun looking in the direction of thearrows on line 44 in FIG. 1;

FIG. 5 is an enlarged section taken on line 55 in FIG. 2;

FIG. 6 is a perspective view, partly broken away, of an open chamberammunition round which may be fired in the recoilless open chamber gunof the invention;

FIG. 7 is a longitudinal section through a modified open chamberammunition round which may he fired in the present open chamber gun, theammunition round in this case containing a conventional recoillesscartridge;

FIG. 8 is an enlarged fragmentary longitudinal section through amodified recoilless open chamber gun according to the invention;

FIG. 9 is a perspective view of a recoilless rotary barrel open chambergun according to the invention; and

FIG. 10 is a longitudinal section through the gun of FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In general terms, the inventionprovides a recoilless open chamber gun, represented in the drawings bythe gun 10, having an open chamber breech mechanism 11 including abreech frame 12 containing a chamber 14. Rotatably supported on theframe within the chamber, for rotation on an axis 16, is an open chambercarrier or cylinder 18. Chamber 14 opens laterally through oppositesides of the frame to form ammunition infeed and cartridge case ejectionopenings for the carrier, as explained below.

Extending forwardly from the front end of the breech 12, in spacedparallel relation to the cylinder axis 16, is a barrel 20 containing abore 22. The rear end of the bore opens to the chamber 14, inconfronting relation to the front end of the breech cylinder 18.Cylinder 18 contains a longitudinal firing chamber 24 which openslaterally through the circumference and longitudinally through the frontend of the cylinder. Extending coaxially from the rear end of thecylinder, and rotatably through the rear end of the breech frame 12, isa shaft 26 by which the cylinder may be rotated or oscillated tosequentially locate its firing chamber 24 in ammunition infeed, firingand cartridge case ejection positions. When the firing chamber is ininfeed position, the open side of the chamber registers with theammunition infeed opening in the breech frame 12 for receiving throughthe opening an ammunition round 30 to be fired. In the simplified breechmechanism illustrated, this infeed opening is defined by one open sideof the chamber 14. When in firing position, the open side of the firingchamber is closed by the breech frame firing strap 32, and the firingchamber is coaxially aligned with and opens forwardly to the gun bore22. When in ejection position, the open side of the firing chamberregisters with the cartridge case ejection opening in the breech framewhich in this instance, like the infeed opening, is defined by one openside of the chamber 14. Breech mechanism 11 is equipped with firingmeans 36, such as a conventional firing pin mechanism, for firing theround 30 in the firing chamber 24 when the latter occupies its firingposition.

As thus far described, the open chamber gun is conventional. Accordingto the present invention, the gun is equipped with rearwardly openingventuri means 38 and with passage means 40 for communicating the venturimeans to the firing chamber 24 when the latter occupies its firingposition. During firing of an ammunition round 30 in the gun, a portionof the high pressure propellant gas generated by the burning propellantcharge in the round issues at high velocity through the venturi means 38to produce a forward, counter-recoil thrust on the gun. Thecounter-recoil means, consisting of the venturi means 38 and passagemeans 40, are so constructed and arranged that the magnitude of thiscounter-recoil thrust is substantially equal to the rearward, recoilforce exerted on the gun during firing. Accordingly, during firing thepresent open chamber gun is subjected to substantially equal andopposite recoil and counter-recoil forces, whereby the gun exhibits arecoilless firing action.

In the particular, recoilless open chamber gun 10 of the invention whichhas been selected for illustration in FIGS. 1-5 the counter-recoilventuri means 38 comprise three separate venturis 42, 44, and 46 whichare generally circularly curved in cross-section about axes whichparallel the axis of the cylinder 18. The passage means 40 comprisethree separate gas passages or plenums 48, 50, and 52 which communicatethe venturis 42, 44, and 46, respectively, to the firing chamber 24.Plenum 48 extends longitudinally through the breech frame firing strap32 and opens laterally to the chamber 14 through a number oflongitudinal spaced ports 54 in the inner wall of the strap. The rearend of this plenum opens to the breech venturi 42. Plenums 50 and 52extend longitudinally through the breech cylinder 18, at opposite sidesof the firing chamber 24, and open laterally to the firing chamberthrough a number of ports 56 in the side walls of the chamber. When thefiring chamber occupies its firing position, the rear ends of thecylinder plenums 50, 52 register with and open to the breech venturis44, 46.

The operation of the illustrated recoilless open chamber gun 10 of theinvention is believed to be obvious from the preceding description.Thus, when an ammunition round 30 is to be fired in the gun, the breechcarrier or cylinder 18 is rotated to locate its firing chamber 24 ininfeed position and the round is introduced laterally into the chamber.The cylinder is then rotated to locate the firing chamber in firingposition, and the round is fired by actuation of the breech firing means36. A major portion of the propellant gas generated within the firingchamber during such firing propels the projectile of the round forwardlythrough the gun bore 22. The remaining propellant gas flows from thefiring chamber through the plenum ports 54, 56 and the propellant gasplenums 48, 50, 52 to the breech venturis 42, 44, 46 and then exits athigh velocity through these venturis to produce on the gun acounter-recoil thrust substantially equal and opposite to the recoilforce exerted on the gun as a consequence of forward propulsion of theprojectile from the gun. In this regard, it will be understood that theventuris 42, 44, 46, plenums 48, 40, 52 and ports 54, 56 are so sizedthat the counter-recoil thrust produced by the propellant gas issuingthrough the venturis substantially equals the recoil force on the gunduring firing.

At this point, it is significant to recall that a variety of ammunitionrounds may be fired in the present recoilless open chamber gun. Theammunition round 30, for example, is also called semi-co bustible openchamber ammunition round of the type disclosed in the aforementionedcopending application Ser. No. 665,136, entitled Semi-CombustibleAmmunition for Open Chamber Breech Mechanism. This round comprises ayieldable, noncombustible plastic cartridge case 58 (FIG. 6) containing21 propellant charge 60 and a projectile 62.

As is characteristic of open chamber guns and ammunition of the kindunder discussion, the cylinder firing chamber 24 and the ammunitioncartridge case 58 have complementary, generally triangular round shapesin cross section. This particular firing chamber and ammunition shapehas several advantages which are fully explained in the aforementionedprior art patents. Accordingly, these advantages will not be repeatedhere. Suffice it to say that the two side walls of the firing chamber 24and the three sides of the ammunition cartridge case 58 arecylindrically rounded to the same radius of curvature as thecircumference of the breech cylinder 18. Accordingly, when theammunition round 30 is positioned in the firing chamber, the side of theround which is exposed in the open side of the firing chamber issubstantially flush with the cylinder circumference. The inner Wall ofthe breech frame firing strap 32 is cylindrically curved to the sameradius and slidably engages the circumference of the breech cylinder.Accordingly, when the round 30 is rotated to firing position, theexposed wall of the round seats flush against the inner Wall of thefiring strap. In the particular semi-combustible ammunition underconsideration, the three sides of the cartridge case 58 are formed withopenings 64 which uncover or expose the plenum ports 54, 56 in thebreech mechanism 11 when the firing chamber occupies its firingposition. It is now evident, that when the round 30 is fired in the gun,a portion of the propellant gas is permitted to flow from the firingchamber, through the ports 54, 56, into the breech plenums 48, 50, 52.and then through these plenums to the breech venturis 42, 44, 46 in themanner explained above. As discussed in the last-mentioned copendingapplication, the propellant gas generated within the cartridge case 58during firing expands the case the elfect sealing of the breechinterfaces against propellant gas leakage.

Among the other types of ammunition which may be fired in the presentrecoilless open chamber gun is the caseless ammunition disclosed in theaforementioned copending application, Ser. No. 671,910, entitled SealedOpen Chamber Breech Mechanism and Caseless Ammunition Therefor. In thiscase, it will be understod that the breech mechanism will be equippedwith suitable obturator means, such as the obturator means disclosed inthe application, for sealing the breech interfaces against propellantgas leakage during firing. Moreover, since the ammunition is caseless,the need for rotating the firing chamber 24 to ejection position afterfiring is eliminated. FIG. 7 illustrates a round 65 of yet another typeof open chamber ammunition which may be fired in the present recoillessopen chamber gun. In this case, the ammunition is like that disclosed inthe aforementioned copending application Ser. No. 665,160, entitled,Ammunition Improvements To Permit Firing of a Conventional ClosedChamber Cartridge in an Open Chamber Breech Mechanism, and comprises astandard recoilless ammunition cartridge 66 contained within a plasticadapted sleeve or jacket 68.

This jacket has side openings 70 which expose the propellant gas ports72 in the cartridge case 74 of the recoilless cartridge 66. Theammunition jacket 68 has the same external, generally triangular roundshape in cross section as the round 30 and is designed to permit firingof the standard recoilless cartridge 66 in an open chamber gun.

Reference is now made to FIG. 8 illustrating a modified recoilless, openchamber gun according to the invention and a round 102 of modifiedrecoilless ammunition to be fired in the gun. Gun 100 is basicallyidentical to the gun 10 described earlier and, accordingly, need not beexplained in detail. Sufiice it to say that the guns differ only intheir respective counter-recoil thrust producing means. Thus, themodified gun 100 is provided with rearwardly opening venturis 104 in therear end of the breech frame 106 which communicate forwardly to thebreech cylinder firing chamber 108,.when the latter occupies itsillustrated firing position. The recoilless ammunition round 102 has aplastic cartridge case 112 of the same generally triangular round shapein cross section as the earlier described rounds. This cartridge casecontains a propellant charge 114 and a projectile 116. In contrast tothe earlier described ammunition rounds, however, the sides of thecartridge case 112 are completely closed and the rear end wall of thecase is provided with ports containing blowout plugs 118 which registerwith the venturis 104 when the ammunition round 102 is located in firingposition. When the ammunition round is fired, propellant gas pressureblows the plugs 118 rearwardly through the venturis 104 to permit aportion of the propellant gas to issue at high velocity through theventuris and thereby produce a counter-recoil thrust on the gun. As inthe earlier embodiment of the invention, the venturis 104 are so sizedthat this counter-recoil thrust is substantially equal to the recoilforce exerted on the gun during firing.

All of the open chamber guns described thus far have fixed barrels whichare secured to and remain stationary with the breech frame. Theaforementioned Patent No. 3,041,939 discloses another type of openchamber gun referred to herein as a rotary barrel open chamber gun. Inthis type of gun, the barrel or barrels are fixed to and rotate with thebreech carrier or cylinder. The cylinder and barrels undergo continuousrotation, even during firing, whereby the gun is characterized by anextremely high firing rate. FIGS. 9 and 10 illustrate a recoillessrotary barrel open chamber gun 200 according to the invention. Gun 200has a breech frame 202 including a central portion 204 and integralcoaxial flange-like bearing rings 206, 208 at the front and rear ends ofthe central frame portion. Within the breech frame, on the common axisof the bearing rings 206, 208, is a cylinder receiving chamber 210.Chamber 210 opens longitudinally through the front and rear ends of thebreech frame and laterally through opposite sides of the central frameportion 204. As in the earlier embodiments of the invention, the sideopenings in the breech frame 202 provide lateral ammunition infeed andejection openings to the cylinder receiving chamber.

Rotatable within and on the axis of the chamber 210 is a carrier orcylinder 212. The front and rear ends of this cylinder are exposedthrough the central openings in the bearing rings 206, 208. Breechcylinder 210 is rotatably supported on the breech frame 202 by a pair ofbearing units 214 which surround the ends of the cylinder in the planesof the bearing rings, respectively. Breech cylinder 212 contains anumber of uniformly spaced longitudinal firing chambers 216. Each firingchamber opens laterally through the circumference of the cylinder in theregion between the breech frame bearing rings 206, 208. Each firingchamber is thus bounded at its ends by front and rear end walls 218,220, respectively.

Associated with each firing chamber 216 is a gun barrel 222. Each barrelis secured to the front end wall 218 of its respective firing chamber,as by being threaded in the wall, in such a way that the bore 224contained in the barrel is coaxially aligned with and opens rearwardlyto the firing chamber. It is now evident, therefore, that the gunbarrels 222 are rotatable with the breech cylinder 212.

At the rear end of the breech frame 202 is a motor 226 for driving thebreech cylinder 212 continuously in unidirectional rotation. During thisrotation, the cylinder firing chambers 216 rotate through ammunitioninfeed, firing, and ejection positions. When in infeed position, theopen side of each firing chamber registers with the breech frameammunition infeed opening to permit lateral infeed movement of anammunition round 228 to be fired into the chamber from ammunition infeedmeans (not shown). In firing position, the open side of each firingchamber is closed by the breech frame firing strap 230 to permit firingof the ammunition round in the chamber. It will be understood that arotary barrel gun may have more than one firing station and acorresponding number of firing straps. For convenience, it is assumedthat the illustrated gun has a single firing station. When in ejectionposition, the open side of each firing chamber registers with the breechframe ejection opening to permit lateral ejection of the spent cartridgecase of a fired round or an unfired round.

The opening chamber gun 200 is equipped with firing means 232 for firingeach ammunition round 228 in firing position. The illustrated firingmeans are assumed to be electrically actuated firing means which areenergized in firing position by engagement of contacts 233a on thecylinder 212 for each firing means with energizing contacts 23% on thefiring strap 230.

It will be recognized that the open chamber gun 200 is generallyconventional as it is thus far described. During operation of the gun,the breech cylinder 212 is driven continuously in rotation to rotate itsfiring chambers 216 in succession through infeed, firing, and ejectionpositions. Each firing chamber receives an ammunition round 228- infiring position, the round is fired in firing position, and the spentcartridge case of the round is ejected in ejection position. The gunbarrels 222 rotate with the breech cylinder, as already noted, wherebythe cylinder can continue to rotate during firing to provide the gunwith a high firing rate capability.

According to the present invention, the gun 200 is improved by providingthe same with a counter-recoil action similar to that described above inconnection with the gun of FIG. 8. To this end, the ammunition rounds228 which are fixed in the gun 200 are identical, except for theelectrical primer in the latter rounds, to the ammunition rounds 102which are fixed in the gun of FIG. 8. Also, the rear end wall 220 ofeach firing chamber 216 in the gun 200 is provided with rearwardlyopening venturis 234- which register with the blowout plugs 236 of anammunition round 228 contained in the respective firing chamber.Accordingly, during firing of each round in the gun 200, a portion ofthe high pressure propellant gas generated within the round exitsthrough the venturis 234 of its firing chamber to produce acounter-recoil thrust on the gun, all in essentially the same manner asdescribed earlier in connection with FIG. 8. The rotary barrel openchamber gun 200, therefore, has a recoilless firing action. The cylinderdrive motor 226 is attached to the rear end of the breech frame 202 insuch a way that the motor uncovers the venturis of each firing chamber216 in firing position, as shown.

At this point, it will be evident to those versed in the art that whilethe invention has been disclosed in connection with open chamber gunshaving rotary open chamber carriers or cylinders, the recoilless firingfeatures of the invention may be embodied, as well, in an open chambergun having a so-called breech mechanism.

In this type of open chamber breech mechanism, the firing chamber orchambers are contained in separate open chamber carriers supported by aconveyor of some type which is driven endwise through the breech frameto locate each firing chamber in infeed, firing, and ejection positions.

What is claimed as new in support of Letters Patent is: 1. A recoillessopen chamber gun comprising: a breech frame containing a chamber; acarrier supported on said frame within said chamber for rotation on anaxis; said frame having an ammunition infeed opening to said chamberbetween the ends of said carrier, and rearwardly opening venturi means;said carrier containing a longitudinal firing chamber opening laterallythrough the circumference of said carrier and longitudinally through thefront end of said carrier; a barrel extending forwardly of said frame inspaced parallel relation to said carrier axis; said carrier beingrotatable in said breech chamber to locate said firing chamber in anammunition infeed position, wherein the open side of said firing chamberregisters with said infeed opening to receive a round of ammunitionthrough said opening, and a firing position, wherein the open side ofsaid firing chamber is closed by said breech frame and said firingchamber opens forwardly to the bore on said barrel to condition said gunfor firing said round to generate a high pressure propellant gas in saidfiring chamber; there being passage means communicating said firingchamber and venturi means in firing psition, whereby a portion of saidpropellant gas issues at high velocity through said venturi means duringfiring of said round to produce on said gun a counter-recoil thrustopposing the recoil force exerted on said gun during firing; and saidpassage means comprising a plenum extending longitudinally through saidcarrier along one side of said firing chamber and opening laterally tosaid firing chamber through a sidewall of said firing cham ber, and saidplenum communicating with said venturi means when said firing chamberoccupies said firing position. 2. A recoilless open chamber guncomprising: a breech frame containing a chamber; a carrier supported onsaid frame within said chamber for rotation on an axis; said framehaving an ammunition infeed opening to said chamber between the ends ofsaid carrier, and rearwardly opening venturi means; said carriercontaining a longitudinal firing chamber opening laterally through thecircumference of said carrier and longitudinally through the front endof said carrier; a barrel extending forwardly of said frame in spacedparallel relation to said carrier axis; said carrier being rotatable insaid breech chamber to locate said firing chamber in an ammunitioninfeed position, wherein the open side of said firing chamber registerswith said infeed opening to receive a round of ammunition through saidopening, and a firing position, wherein the open side of said firingchamber is closed by said breech frame and said firing chamber opensforwardly to the bore in said barrel to condition said gun for firingsaid round to generate a high pressure propellant gas in said firingchamber; there being passage means communicating said firing chamber andventuri means in firing position, whereby a portion of said propellantgas issues at a high velocity through said venturi means during firingof said round to produce on said gun a counter-recoil thrust opposingthe recoil force exerted on said gun during firing; and

said passage means comprising a pair of plenums extending longitudinallythrough said carrier along opposite sides of said firing chamber andopening laterally to said firing chamber through the sidewalls of saidfiring chamber, and said plenum communicating with said venturi meanswhen said firing chamber occupies said firing position.

3. A recoilless open chamber gun comprising:

a breech frame containing a chamber;

a carrier supported on said frame within said chamber for rotation on anaxis;

said frame having an ammunition infeed opening to said chamber betweenthe ends of said carrier, and rearwardly opening venturi means;

said carrier containing a longitudinal firing chamber opening laterallythrough the circumference of said carrier and longitudinally through thefront end of said carrier;

a barrel extending forwardly of said frame in spaced parallel relationto said carrier axis;

said carrier being rotatable in said breech chamber to locate saidfiring chamber in an ammunition infeed position, wherein the open sideof said firing chamber registers with said infeed opening to receive around of ammunition through said opening, and a firing position, whereinthe open side of said firing chamber is closed by said breech frame andsaid firing chamber opens forwardly to the bore in said barrel tocondition said gun for firing said round to generate a high pressurepropellant gas in said firing chamber;

there being passage means communicating said firing chamber and venturimeans in firing position, whereby a portion of said propellant gasissues at high velocity through said venturi means during firing of saidround to produce on said gun a counter-recoil thrust opposing the recoilforce exerted on said gun during firing;

said breech frame including a firing strap which closes the open side ofsaid firing chamber when said firing chamber occupies said firingposition; and

said passage means comprising a plenum extending longitudinally throughsaid firing strap and opening laterally to said breech chamber throughthe inner wall of said firing strap for communication of said plenumwith said firing chamber when said firing chamber occupies said firingposition, and said plenum communicating with said venturi means.

4. A recoilless open chamber gun comprising:

a breech frame member containing a chamber,

a carrier member supported on said frame member within said chamber forrotation on an axis,

said frame member having an ammunition infeed opening to said chamberbetween the ends of said carrier member and rearwardly opening venturimeans,

said carrier member containing a longitudinal firing chamber openinglaterally through the circumference of said carrier member andlongitudinally through the front end of said carrier member,

a barrel extending forwardly of said frame member in spaced parallelrelation to said carrier axis,

said carrier member being rotatable in said breech chamber to locatesaid firing chamber in an ammunition infeed position, wherein the openside of said firing chamber registers with said ammunition infeedopening to receive a round of ammunition through said opening, and afiring position, wherein the open side of said firing chamber is closedby said breech frame and said firing chamber opens forwardly to the borein said barrel to condition said gun for firing said round to generate ahigh pressure propellent gas in said firing chamber, and

there being passage means communicating said venturi means and firingchamber in firing position, whereby a portion of said propellant gasissues at high velocity through venturi means during firing to produce acounter-recoil thrust on said gun opposing the recoil force exerted onsaid gun during firing, said passage means including a plenum extendinglongitudinally through each of said members and opening laterally tosaid firing chamber when said firing chamber occupies its firingposition.

5. A recoilless open chamber gun comprising: a breech frame containing achamber, a cylinder supported on said frame within said chamber forrotation on an axis,

a barrel secured to and extending forwardly from the front end of saidframe in spaced parallel relation to said axis and containing a boreopening rearwardly to said chamber in confronting relation to the frontof said cylinder,

said breech frame having a lateral ammunition infeed opening to saidchamber between the ends of said cylinder, rearwardly opening venturimeans in the rear end of said frame, and a firing strap,

said cylinder containing a firing chamber opening laterally through thecircumference of said cylinder and longitudinally through the front endof said cylinder,

said cylinder being rotatable in said frame to locate said firing straphaving a plenum extending longitudinally through said strap andcommunicating with said venturi means, and ports extending laterallyfrom said plenum through the inner wall of said firing strap forcommunication with said firing chamber when said firing chamber occupiessaid firing position, and

said cylinder containing a pair of plenums extending longitudinallythrough said cylinder at opposite sides of said firing chamber andcommunicating with said venturi means in firing position, and portsextending laterally from said cylinder plenums through the sidewalls ofsaid firing chamber, whereby a portion of said propellant gas issues athigh velocity through said venturi means to produce a counterrecoilthrust on said gun opposing the recoil force exerted on said gun duringfiring.

6. A recoilless open chamber gun for firing open chamber ammunitionrounds each having a generally triangular round shape in transversecross-section, comprising:

a barrel containing a bore;

an open chamber breech mechanism at the breech end of said barrelincluding a breech frame containing a chamber and a lateral ammunitioninfeed opening to said chamber, an ammunition carrier positioned withinsaid chamber and containing a longitudinal firing chamber of generallytriangular round shape in transverse cross section openinglongitudinally through the front end and laterally through thecircumference of said carrier, and means supporting said carrier on saidframe for rotation between an ammunition infeed position wherein theopen side of said firing chamber registers with said infeed opening topermit lateral infeed movement of an open chamber ammunition round intosaid firing chamber and a firing position wherein the open side of saidfiring chamber is closed by said frame and said firing chamber iscoaxially aligned with and opens forwardly to said bore to conditionsaid gun for firing an ammunition round in said firing chamher togenerate a high pressure propellant gas in said firing chamber;

said breech mechanism having rearwardly opening venturi means andpassage means communicating said venturi means and firing chamberrinfiring position, whereby a portion of said propellant gas issues at highvelocity through said venturi means during firing to produce on said guna counter-recoil thrust opposing the recoil force exerted on said gunduring firing; and

said passage means opening laterally to said firing chamber in firingposition between the ends and through at least one longitudinal side ofsaid firing chamber.

7. An open chamber gun according to claim 6, wherein:

said passage means open laterally to said firing chamber through atleast two longitudinal sides of said firing chamber.

1 2 References Cited UNITED STATES PATENTS 4/1957 Bird 4239.5 X 7/1957Atherton 89--1.803 12/1958 Dardick 42-39.5 4/1962 Musser 89--1.706

FOREIGN PATENTS 9/1949 Switzerland.

SAMUEL w. ENGLE, Primary Examiner.

US. Cl. X.R.

